Electric-current shunt.



W. H.4 PRATT. ELECTRIC CURRENT SHUNT. APPLICATION FILED FEB.. 3, .1911?.

Patented Oct. 20, 1914.

wim eases.

UNITED STATES EPATENT oEEToE.

WILLIAM I-I. PRTT, OF LYNN, 1\/IASSACHUSEIYIIS, ASSIGNOR, TO GENERAL' ELECTRIC COMPANY, A CORPORATION 0F NEW YORK.

ELECTRIC-*CURRENT SKU-NT.

Specification of Letters Patent. i

Patented Oct. 20, 19141:.

Application filed February 3, 1913. Serial No. 746,004.

cation.

My invention relates to electric current" shunts, and more particularly to current shunts for use in connection with electrical f measuring instruments.

My invention is particularly adapted for use with instrumentsemployed in indicating or recording the 'charge and discharge conditions of storage batteries, and I have accordingly chosen in the `following specification thislapplication of my invention for the purposes of illustration.

The objects of my invention are to pro- Vide a novel and improved construction of electric current shunt, and more specilcally a current shunt particularly adapted for use with a battery charging and dischargin'instrument.

urther objects of my inventlon are to provide a current shunt for the abovementioned purpose which may be readily and accurately adjusted to compensate for the 30 difference in energy supplied to a storage battery during charge and taken from the battery during discharge.

The novel features which I believe to be characteristic of my invention will be indicated in the claims appended hereto.

The features of construction and mode of operation will be understood from the following description taken in connection with the accompanying drawings which show preferred .embodiments of my invention,

Figure 1 is a diagrammatic representation of the novel features of my invention in its. 'application to a battery charging and discharging instrument; Fig. 2 is an elevation of a preferred form of my improved shunt;

f Fig. 3 is a sectional elevation of the shunt 'age battery in charging is always in excess of that taken from the battery on discharge. In indicating or recording the charge and discharge conditions of a storage battery, it is customary to employ an instrument which is automatically compensated for the difference between the amount of energy put into the battery and the amount taken out. This compensation is generally provided by giving to the instrument a different rate of registration on discharging than its rate of ,registration on charging. The electriccurrent shunt of my invention provides a ready Zand accurate means for this compensation `'of a battery charging and discharging instrument, 'as will be better frefefrence to Fig. 1 of the drawings.

j In Fig. l of the drawings there is dia-' grammatically represented a storage batitery B adapted to be connected to either a @generator Gr or a motor M by means of switches S and S. `When the switch S is elosed and the switch S open, as indicated in the figure, the battery is connected to the generator and is being charged. On the other hand, when the switch S is closed and lthe switch S open, the battery is connected .to the motor M and is discharging.

For the purpose of illustration, I have employed a mercury motor .ampere-hour Imeter. It will be understood, however, that t:my invention is in no sense limited to this `particular type of instrument. The meter illustrated is similar in construction to that described in my prior Patent No. 993,872, dated May 30, 1911, and comprises a retainving chamber 1'0 containing a body of mer# cury 1l. IVithin the chamber and submerged in the mercury is a cup-shaped armature 12 which is rigidly secured to the rotatable meter shaft 13. The mercury l1 and cupshaped armature 12 are located within the field influence of la permanent magnet whose poles are indicated by referencevcharactcrs 14.. Cur'rent is conducted to the mercury within theretaining chamber by elec -trodes l5 electrically vconnected by conductors 16 to terminals y17 of my novel and improfved electric current shunt. N

f The current shunt diagrammatically illustrated in Fig. 1 of the drawings is shown Iin greater detail in Figs. .tand 5. By refunderstood by erencefto these figures, it willvbje seen that rent in the derived circuit to that in the 65 the shunt comprises a substantially" triai'igu-` supply circuit is capable of adjustment.

lar sheet or member 'of iesistaiee material From a consideration o- Fig. 1 it will be 1S.v provided `with two relatively fixed tr= apparent that when the battery B is dis-v mirials 17; Auxiliary 'strips ornienibers of charging through the motor M the relative resistance material i9 are' electi'ically'ncon# potential drop across the shunt terminals 70 nected between one of the teri'iiii'ials 17 and l7e=17 will be at its maximum, so that the the third corner 20 of the' sheet et resistai'ice meter will have its highest speed or rate of material 18. An adji'is'table centaet member registration under this condition. When 2i is arranged to slide iii contact with the the battery is charging the current enters at strips ofy resistance ,materialv 19 and is' tli'eutern'iinal 24 and distributes itself in two 75 mounted lon a 'guide bar 22. y The contact paths, a" portion going toward the adjacent member21 be operatively secured to terminal 17 and a portion toward the corner the bar 22 desired position by means 20. By regulating the position of the conof a bolt 23.w The resistance sti-ips 1i-9 are tact member 21, the 'relative drop in potenthus, through Ythe medium ot. the ci'in'taettial between the terminals 17-117, is adjust- 80 member 21 and the bar 22 eleetificallycon# able.- By this arrangement it is possible to' nected to the third terminal 24 of tie sl'iunt.- make a. correct compensation for the excess Referring again more specificall to Fig'. amount of current supplied to the battery l of' the drawings, it will be seen that the in charging. This correction oi' compensa-- fixed teliiiinals 17 are connected to the tcition can be adjusted to allow for losses in 85 ininals of the instrument, the electric cirthe battery and also for any disturbance in c uit of which is referred to hereinafter as the average meter speed due to the lighter the derived circuit. When the switch S is load at which the charge will be iegttled closed and the switch S open ,the terminals in comparison to the discharge. l* 17 are also connected to the circuit includ- Figs. 2 and 3 illustrate another consti'iic- 9;. ing the battery B and motor M, which is tion of shunt embodying the novel features referred to hereinafter for convenience as of my invention. The main sheet or mein.-`| tlie supply circuit. ber of resistance material 25 of thiscon; When the switch S is closed and the struction of shunt is also of substantially switch S open the relative drop in potential triangular shape.y Strips of resistance mate- 95 between the terminals 17--17 will bc conrial 26 are ii'itegrally connected with the etant. I have employed the expression rclamain memberof resistance material 25 and tive potential drop to designate the drop in are separated from one another by a sectorpotential between the terminals 17-17 in shaped guide slot 27. A contact bolt 28 is its relation to the current in the derived ciroperatively mounted in the slot 27 and is 100 cuit and the current in the supply circuit. carried by a pivctcd larm 29. The arm 29 is By constant relative drop in potential l pivotcd to a fixed part 30 and is provided at mean that the drop in potential between the its upper end with a terminal 31. It will terminals 17--17 is such that the ratio of the thus be seen that thc arm 29 can be turnedz cui-rent in the derived circuit to that in the about its pivot and the contact bolt 28 se- 105 Supply circuit is constant and incapable of cured in any desired position in the guide adjustment. vslot 27. It will be understood that the bolt The third and adjustable terminal 24 of 28 and arm 29 serve to electrically connect tle shunt is connected to thc supply circuit the strips of resistance material 26 to the which includes the generator Gr and battery terminal 31. As illustrated in Fig. B of the 110 B. lt will thus be evident that the terminal drawings, I may employ a plurality of re- 24 lis einptoyed only when the switch S is sistancemembersv 25 and 26 which thus closed and the switch S open, as indicated in serve to increase the capacity of the shunt. Fig. 1 of the drawings. y adjusting the In the drawings l have shown three resistposition ol the contact member 21 on the ance members connected in parallel. A 115 i strips of resistance material 19 the resistance sleeve 35 is secured to the arm 29 and carries of the shunt between the adjustable terminal three circular spacing washers 36 which 24 and the fixed terminals 17-17 may be sci-ve to suitably space the resistance memvaricd vand in this manner the proportion et bers from one another and from the arm 29.

the main supply current which is shunted to The bolt 28 is screw threaded in the sleeve 120 the derived or .instrument circuit may be and serves to firmly bind the strips 26, controlled. The adjustment of the contact thespacing washers 36 and arm 29 together member 21. thus serves to vary the relative in the desired adjusted position. The shunt potential drop between the terminals 17-17; `illustrated in this figure is provided with that is, for a constant supply current the fixed terminals 32 corresponding to the ter- 125 potential drop between the terminals 17"-17 minals 17 of the construction oi shunt shown can be varied by adjusting the contact incinin Figs. 1, `'land fi. l

beil 2-1. In other words the ratio of the cui'- While l haveshownj certain forms ot con struction by which my invention maybe carried out, Ido not desire to.v limit myself to these particular forms of construction, but seek in the appended claims to cover all modifications thereof which will be obvious to those skilled in the art and which are.

within the scopeof my invention.-V

lVhat I claim as new and desire to secure by Letters Patent of the United States, is

l. An electric current shunt comprising a member of resistance material having two terminals f or connection -to a derived circuit, an auxiliary member of resistance material electrically connected to said first men,-

three terminals connected by 'resistance material, two of said terminals being designed for connection toa derived circuit and the third terminal for connection to a supply circuit, the resistance between said two terminals being constant, and means whereby the third terminal may be adjusted to vary the resistance between the third terminal nd the other two terminals.

4. An electric current shuntcomprising a member of resistance material having two terminals for supplying current to a derived circuit, a third terminal operatively related to said member and adapted for connection to a supply circuit, and means whereby said l third terminal. may be adjusted to vary the relative potential drop between Said two first mentioned terminals.

5. A. current shunt for an electrical measuring instrument comprising an integral member of resistance material, two terminals on said member arranged for connection .to the terminals of the instrument,-and a third terminal on said member arranged to form a triangle with said other two terminals. j 6. A. current shurit for an electrical measuring instrument comprising -an integral member of resistance material, two terminals on said member arranged for connection to the terminals of the instrument, and a third terminal on said member arranged for connection to a supply circuit and so positioned that the supply current will liow from said third terminal through said member in `two directions and toward each of said two irst mentioned terminals.'v

7. A- current shunt. for electrical apparatus comprising two relatively fixed terminals for connection to the terminals of the apparatus, a thirdgterxninal for-connectionr to a supply circuit, resistance material elec`v ftrically connecting said terminals, and.

means whereby said third terminal may be e adjusted to vary the relative drop in potential between said fixed terminals.

8. An electric .current shunt comprising av substantially triangular shaped member ofv resistance material, fixed terminals near two of thecorners of said member, an auxiliary member` of resistance' material connecting the third corner and one of the other corners of said triangular shaped member and an adjustable terminal connected to said auxiliary member- 9. An electric cilrrent shunt comprising a member of resistance material having two terminals, en auxiliar member of. resistancematerial electrica ly connected to saidV first mentioned member, anda pivoted arm electrically connected. to said auxiliary member and adapted to be turned about its pivot for adjusting its position on said auxiliary member.

10. An electric current shuntV comprising a member of resistance material having two terminals, an auxiliary member of resistance material integrally connected to said irst mentioned member -and having a guide slot therein, a contactelement operatively positioned in said slot, a pivoted arm con,

nected to said element and arranged to move said element in said slot, a terminal onsaid arm, and means for securing said element at any desired position in said slot.

11. An electric current shunt comprising a member of resistance material having two terminals each arranged for connection to a derived circuit and to a supply circuit, a third terminal electrically related to said member, means whereby the connection of one 'of said terminals to the supply' circuit.

may be severed and a second .supply circuit connected to the third terminal, and means whereby the position of said third terminal may be adjusted to vary the'relative poten- J` tial drop between said two first mentioned terminals when said third terminal is connected tothe second supply circuit." 12. An electric current shunt comprising a member of resista-nce material having two.'

terminals each arranged for connection to4 a derived circuit and to a supply circuit, an auxiliary member of resistance material electrically connected to said iirst mentioned member, a third terminal coperating with said auxiliary member, means whereby the connection of one of said first mentioned terminals to the supply circuit may loesev.

ered 4and a second supply circuit connected to the thirdterminal, and means whereby the position-of sadthird terminal .may be adjusted for varying the relative potential drop between said two first mentioned terminals when said third terminal is connected to the secondsupply circuit.

In witness whereof, I have hereunto set my hand this Twenty-Fourth day of January, 1913.

WILLIAM H. PRATT.

Witnesses:

JOHN A. MGMANUS, Jr., JAMES E. MINKLER. 

